Mark position measuring method and apparatus

ABSTRACT

The present invention provides a method and apparatus for detecting the position of a first mark disposed inside a variable-pressure chamber using a detector disposed outside the chamber and detecting a second mark on an object disposed inside the chamber using the detector. The position of the second mark relative to the first mark is determined based on the detected positions of the first and second marks.

This application is a divisional application of copending U.S. patentapplication Ser. No. 10/912,100, filed Aug. 6, 2004.

CLAIM OF PRIORITY

This application claims priority from Japanese Patent Application No.2003 289156 filed on Aug. 7, 2003, which is hereby incorporated byreference herein.

FIELD OF THE INVENTION

The present invention relates to a mark position measuring method andapparatus, and more particularly, to measuring of the position of atarget object in an exposure apparatus used in micro-device manufacture.

BACKGROUND OF THE INVENTION

In a semiconductor element or other device manufacturing process, asexposure devices for transferring a mask or reticle circuit pattern ontoa wafer, those that use visible light or ultraviolet light are currentlythe main types. However, as semiconductor circuit patterns become everdenser, the dimensions of the smallest patterns are approaching theresolution limits of exposure using light of the wavelengths describedabove. As a result, exposure methods that use smaller wavelength vacuumultraviolet rays (VUV) and X-rays, or electron beams, have gainedattention. For example, an exposure method using vacuum ultraviolet raysand X-rays is described in Japanese Patent Application Laid-Open No.05-198471.

Vacuum ultraviolet rays (VUV) and X-rays or electron beams experiencelow transmittance in the atmosphere, and therefore in exposure methodsthat use such light or beams, the exposure must be conducted within ahigh vacuum. As a result, carrying out alignment is also subjected tostringent limiting conditions. For example, the wafer that is thedetection target object is placed inside a vacuum chamber, but thesensor that senses an alignment mark must be placed outside the vacuumchamber at an observation window in order to combat the effects ofescaping gas. Therefore, there is a possibility that the optical axis ofthe alignment system optical system might be warped by deformation ofthe chamber housing and observation window due to the difference inpressure between the inside of the chamber and the outside of thechamber, thus leading to an alignment detection error.

SUMMARY OF THE INVENTION

The present invention is conceived in consideration of theabove-described problem, and has as an object to make it possible todetect with high accuracy the position of a mark disposed inside avariable-pressure chamber using a sensor disposed outside the chamber.

In particular, it is an object of the present invention to make itpossible to detect a mark position accurately even if an observationwindow of the chamber is deformed due to the difference in pressurebetween the inside and the outside of the chamber.

According to one aspect of the present invention, there is provided amark position measuring method comprising: a first measuring step ofmeasuring a position of a first mark disposed inside a variable-pressurechamber using a detector disposed outside the chamber and a secondmeasuring step of measuring a position of a second mark disposed insidethe chamber using the detector, wherein a position of the second markrelative to the first mark is determined based on the positions of thefirst mark and the second mark detected in the first measuring step andthe second measuring step, respectively.

Moreover, according to the present invention, an alignment detectionapparatus for implementing the above-described position measuring methodis provided.

Further, according to the present invention, an exposure device forexecuting alignment detection or calibration detection based on theabove-described mark position measuring method is provided.

Other features, objects and advantages of the present invention will beapparent from the following description when taken in conjunction withthe accompanying drawings, in which like reference characters designatethe same or similar parts throughout the figures thereof.

BRIEF DESCRIPTION OF THE DRAWINGS

The accompanying drawings, which are incorporated in and constitute apart of the specification, illustrate embodiments of the invention and,together with the description, serve to explain the principles of theinvention.

FIG. 1 is a block diagram showing the schematic structure of an exposuredevice according to a first embodiment of the present invention;

FIGS. 2A, 2B and 2C are diagrams illustrating detection methodsaccording to a first embodiment and a second embodiment of the presentinvention;

FIG. 3 is a diagram illustrating an example of an alignment markaccording to the first and second embodiments of the present invention;

FIG. 4 is a diagram illustrating an example of an alignment markaccording to a third embodiment and a fourth embodiment of the presentinvention;

FIGS. 5A and 5B are diagrams illustrating detection methods according toa third embodiment and a fourth embodiment of the present invention;

FIG. 6 is a diagram showing a schematic structure of an exposure deviceaccording to a fifth embodiment of the present invention;

FIGS. 7A and 7B are diagrams showing examples of marks whose positionscan be detected along two axes simultaneously;

FIG. 8 is a diagram showing a schematic structure of an exposure deviceaccording to a sixth embodiment of the present invention;

FIG. 9 is a diagram showing another schematic structure of an exposuredevice according to a sixth embodiment of the present invention;

FIG. 10 is a diagram showing another schematic structure of an exposuredevice according to a seventh embodiment of the present invention;

FIG. 11 is a flow chart illustrating a wafer mark position detectionprocess according to a first embodiment of the present invention;

FIG. 12 is a flow chart illustrating a wafer mark position detectionprocess according to a second embodiment of the present invention;

FIG. 13 is a flow chart illustrating a wafer mark position detectionprocess according to a third embodiment of the present invention; and

FIG. 14 is a diagram showing a device manufacturing process.

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS

Preferred embodiments of the present invention will now be described indetail in accordance with the accompanying drawings.

First Embodiment

FIG. 1 is a block diagram showing the schematic structure of an exposuredevice according to a first embodiment of the present invention. In FIG.1, R designates a reticle, ST designates a wafer stage that can move inthree dimensions and W designates a wafer placed atop the wafer stage.An exposure beam projected from an exposure light source 16 is directedonto the reticle R by mirrors 15, 14. The exposure beam reflected fromthe reticle R according to a drawn pattern is directed onto the wafer Wby mirrors 13, 12, thus transferring the pattern on the reticle R ontothe wafer W.

Reference numeral 1 designates an alignment illumination unit, 2, 3 and4 designate focal optical systems, 5 and 6 designate half mirrors, and 8designates an alignment mark, all disposed inside a chamber 11. Itshould be noted that the alignment mark 8 is fixed at a predeterminedposition inside the chamber 11. Moreover, reference numeral 9 designatesan observation window, 10 designates an image sensing unit, 17designates an A/D converter and 18 designates a position detectionapparatus, with the image sensing unit 10, the A/D converter 17 and theposition detection apparatus 18 disposed outside the chamber 11. Theposition detection apparatus 18, for example, includes a CPU, a ROM anda RAM (not shown), and calculates the mark position from the alignmentmark 8 input from the A/D converter 17 and a wafer mark WM image(two-dimensional digital signal sequence) by the CPU executing a programstored in the ROM. Detection beams for the alignment mark 8 and thewafer mark WM pass through the observation window 9 and reach the imagesensing unit 10, although these detection beams have essentially thesame optical axis. The position detection apparatus 18 turns theillumination units 1, 7, ON and OFF by executing a program stored in theROM and implements a process like that to be described below withreference to the flow chart of FIG. 11.

Below, a description is given of an alignment detection process withreference to the flow chart of FIG. 11.

First, the vacuum chamber 11 is put into a high vacuum state by a vacuumpump (not shown) so as to optimize exposure conditions (step S101).After the air pressure has stabilized, the alignment mark illuminationunit 7 is lit, the alignment mark 8 is illuminated and the alignmentmark 8 position is detected (step S102). FIG. 3 shows a shape of anindex mark, with the disposition of a plurality of rectangular slits SM.A beam of light passing through the index mark 8 is reflected by thehalf-mirror 6 to the image sensing unit 10 through the focal opticalsystem 4 and the observation window 9, so as to form an image on animage sensing surface as shown in FIG. 2A, thus forming an image of theindex marks SM1-SMn on the image sensing surface. The light rays thusfocused are photoelectrically converted at the image sensing unit 10and, thereafter, converted into a two-dimensional digital signalsequence at the A/D converter 17. The positions of the index mark SMrectangular patterns are then detected by the position detectionapparatus 18. The positions of the rectangles can be obtained bycumulatively projecting an image within a window WP in FIG. 2A along theX axis and determining the center of gravity of the image.

Next, the position of the wafer mark is determined (step S103). Whendetermining the position of the wafer mark, the index mark illuminationunit 7 is extinguished and the alignment illumination unit 1 is lit. Thebeam of light projected from the alignment illumination unit 1illuminates the wafer mark WM on the wafer W via the focal opticalsystem 2 and the half mirror 5. The shape of the WM, like that of theindex mark SM, comprises a plurality of aligned rectangular marks. Thebeam of light reflected from the wafer mark WM then passes through thehalf mirrors 5 and 6 to reach the image sensing unit 10 via the focaloptical system 4 and the observation window 9, to focus an image likethat shown in FIG. 2C on the image sensing surface. Thus, an image ofthe wafer mark WM is formed on the image sensing surface. The focusedbeam of light is photoelectrically converted at the image sensing unit10 and, thereafter, converted into a two-dimensional digital signalsequence. Then, at the position detection apparatus 18, the positions ofthe wafer mark WM rectangles are detected. The positions of therectangles are obtained by cumulatively projecting the image within thewindow WP along the X axis and determining the center of gravity of theimage.

From the positions of the wafer mark WM and the index mark SM detectedas described above, the position detection apparatus 18 determines therelative positions of the two marks and aligns the wafer using the indexmark as a reference (step S104). For example, the position detectionapparatus 18 can determine the position of the wafer mark by determiningthe average of the positions of the index marks SM1-SMn of FIG. 2A andthe average of the positions of the wafer marks WM1-WMp of FIG. 2C, andtaking the difference between the two averages. FIG. 2B illustrates asecond embodiment of the present invention and is not described here.

It should be noted that, in the alignment detection described above,even if the chamber housing, as well as the observation window, aredeformed, and the alignment optical system optical axis is warped by thedifference in pressure between the inside of the chamber and the outsideof the chamber, because the index mark is disposed outside the chamber,and because, moreover, the detection optical axes for the index mark andthe wafer mark are substantially the same, index mark and wafer markrelative position detection error, in other words, wafer mark positiondetection error, can be reduced. In a case in which another wafer markposition is to be detected, the process starting from the step S103described above is executed. When detection of the positions of allwafer marks of detection objects is finished, processing ends (stepS105).

As described above, according to the first embodiment of the presentinvention, by using the index mark disposed inside the chamber as areference, it is always possible to detect accurately the alignmentposition of a target object even when the chamber housing andobservation window are deformed and the alignment optical system opticalaxis is warped due to the difference in pressure between the inside ofthe chamber and the outside of the chamber.

Second Embodiment

In the first embodiment, consideration is not given to the occurrence ofnonlinear aberration in the alignment optical system due to thedifference in pressure between the inside and the outside of the chamber(air pressure inside the chamber). A second embodiment makeshigh-accuracy alignment mark detection possible even in the event thatsuch aberration occurs. It should be noted that the configuration of asemiconductor exposure apparatus of the second embodiment is identicalto that of the first embodiment (FIG. 1).

A description is now given of the alignment detection process of thesecond embodiment, while referring to the flow chart of FIG. 12. Itshould be noted that steps that are the same as those for the firstembodiment (FIG. 11) are given the same reference numeral. First, whenthe chamber 11 is at atmospheric pressure, the position detectionapparatus 18 lights the index mark illumination unit 7, senses the indexmark 8 using the image sensing unit 10, and, based on the sensed imagethus obtained, detects the position of the index mark 8 and stores thisindex mark 8 position in a memory, not shown, in the position detectionapparatus 18 (step S201). Then, the chamber 11 is put into a vacuumstate (step S101). After the vacuum state has stabilized, the index markillumination unit 7 is lit, and the index mark position is againdetected (step S102). Then, an offset is calculated based on the indexmark position stored in step S201, and the index mark position obtainedin step S102.

In other words, the positions of the rectangles of the index marks whenthe chamber 11 is at atmospheric pressure are detected and, as shown inFIG. 2B, offsets (offset (SM1), offset (SM2), . . . offset (SMn))occurring due to the difference in pressure between when the chamber isat atmospheric pressure and after the chamber is put into a vacuum stateare calculated. FIG. 2B is a graph showing on the horizontal axis themark detection positions X1 and on the vertical axis the difference(offset (SMi)) in detected values between when the chamber is atatmospheric pressure and after the chamber is put into a vacuum state.From the graph, a correction curve F(X) is obtained using such methodsas polynomial approximation and interpolation. The curve F(X) is theactual correction curve used when detecting a mark on a wafer.

Thereafter, the wafer mark position is detected using the alignmentillumination unit 1 and the image sensing unit 10 (step S103). Then, thewafer mark detected value is corrected using the offset correction curveobtained in step S202 and the relative position of the wafer markrelative to the index mark is corrected using the corrected detectedvalues (step S203). Corrected values for the wafer mark rectanglesWM1-WMp can be obtained from the correction curve F(X).

A more detailed description is now given of the operations of steps S103and S203. In particular, when detecting the wafer mark, the index markillumination unit 7 is extinguished and the alignment illumination unit1 is lit. The wafer mark WM on the wafer is illuminated by a light beamemitted from the alignment illumination unit 1 via the focal opticalsystem 2 and the half mirror 5. As described in the first embodiment, animage of the wafer mark is formed on the image sensing surface of theimage sensing unit 10 (FIG. 2C). The focus light beam isphotoelectrically converted at the image sensing unit 10 and convertedto a two-dimensional digital signal sequence at the A/D converter 17.The position detection apparatus 18 then determines the positions of thewafer mark WM rectangles from the two-dimensional digital signalsequence. Then, using a previously determined correction curve F(X), aposition offset (offset (WM1), offset (WM2), . . . , offset (WMn)) dueto a pressure differential is determined for each of the detectedpositions of the rectangles WM1-WMp, and the detected positions of therectangles are corrected. Then, the position of the wafer mark isdetermined based on the position of the index mark detected when thechamber was at atmospheric pressure and the corrected wafer markdetected position.

It should be noted that, in the second embodiment of the presentinvention, when the difference in pressure between the inside of thechamber and the outside of the chamber changes, the state of deformationof the chamber housing and the observation window, as well as theaberration described above also change, and in such a case, the indexmark position is re-detected. In other words, so long as any change inthe internal-external chamber pressure differential does not exceed apredetermined threshold, then when detecting the position of anotherwafer mark the process described above may be executed starting fromstep S103 (i.e., steps S105, S106). By contrast, if the change in theinternal-external chamber pressure differential does exceed apredetermined threshold, then, when detecting the position of the nextwafer mark, the processing returns to step S102 and is executed fromthat step onward. However, even in a case in which there is no change inthe internal-external chamber pressure differential, detection of theposition of the index mark may be executed at a predetermined timeinterval and the offset correction curve F(X) re-calculated. Moreover,although in FIG. 12, the detection of the position of the next wafer isthe point in the process at which a check is made for any change in theinternal-external chamber pressure differential, the present inventionis not limited to such an arrangement. Thus, alternatively, detection ofany change in the internal-external chamber pressure differential may beconducted at a predetermined interval, and detection of the index markmay be carried out whenever any change exceeding a threshold value isdetected and the correction curve F(X) re-calculated.

Third Embodiment

In a third embodiment of the present invention, the index mark and thewafer mark are detected at the same time, thus enabling correctalignment detection even if there is a change in the internal-externalchamber pressure differential. It should be noted that the basicstructure of the exposure apparatus of the third embodiment is the sameas that of the first embodiment (FIG. 1).

In the third embodiment, an arrangement is used in which the index markand the wafer mark rectangles do not overlap in a state in whichalignment is conducted at a predetermined accuracy. For example, a marklike that shown in FIG. 4 may be used as the index mark and the wafermark (in this case, the width and pitch of the index mark rectangles areequal to the width and pitch of the wafer mark rectangles). However,provided they are disposed relative to each other at detectablepositions, the index mark and the wafer mark patterns need not belimited to the foregoing configuration. Then, when detecting the wafermark, the alignment illumination unit 1 is also lit at the same time asthe index mark illumination unit 7. As a result, an image of the indexmark and an image of the wafer mark are both formed simultaneously onthe image sensing surface of the image sensing unit 10 at mutuallyexclusive positions, as shown in FIG. 5B. (It should be noted that FIG.5A illustrates a succeeding fourth embodiment of the present invention.)The focused light beam is then photoelectrically converted by the imagesensing unit 10, and then converted into a two-dimensional digitalsignal sequence by the A/D converter. The position detection apparatus18 detects the positions of the rectangles of the index mark SM and thewafer mark WM from the digital signal (i.e., the wafer mark and indexmark images). Thus, as with the first embodiment, the relative positionsof the wafer mark WM and the index mark SM are determined, and the waferis aligned using the index mark as the standard of the reference.

FIG. 13 is a flow chart illustrating a wafer mark position detectionprocess according to a third embodiment of the present invention. Afterthe chamber 11 is put into a vacuum state (step S101), when detectingthe position of the wafer mark, as described above, the positions of theindex mark and the wafer mark are detected at the same time (step S301).Then, the relative positions of the index mark and the wafer mark aredetected based on the simultaneously detected positions of the indexmark and the wafer mark (step S302). When detecting the next wafer mark,the process is repeated, starting with step S301 (step S303).

As described above, according to the third embodiment of the presentinvention, as with the first embodiment, it is always possible to detectaccurately the alignment position of a target object even when thechamber housing and observation window are deformed, and the alignmentoptical system optical axis is warped due to the difference in pressurebetween the inside of the chamber and the outside of the chamber.

Further, according to the third embodiment, the rectangles that comprisethe wafer mark and the rectangles that comprise the index mark do notoverlap, and the index mark and the wafer mark that are inside thechamber are sensed at the same time, and the wafer mark position isdetected with reference to the index mark. Thus, even if the pressuredifferential inside and outside the vacuum chamber 11 changes, it isalways possible to detect accurately the relative positions of the waferand index marks.

Further, by using index marks and alignment marks like those shown inFIG. 7A or FIG. 7B, position detection of two axes intersecting atop thewafer can be carried out in a single image sensing. In FIGS. 7A, 7B, theindex mark SM and the wafer mark WM are provided at positions that donot overlap.

Fourth Embodiment

In a fourth embodiment of the present invention, the effects ofnonlinear aberration are eliminated, as with the second embodiment,while adopting the alignment detection technique of the thirdembodiment. In this case, as with the second embodiment, detection ofthe position of the index mark is carried out while the chamber is atatmospheric pressure. Then, after the chamber has been put into a vacuumstate, the positions of the wafer mark WM and the index mark SM aredetected simultaneously using the same technique as that of the thirdembodiment described above.

As shown in FIG. 5A, a correction curve F(X) for correcting an offsetproduced by a difference in pressure is created using index mark 8detected values. The index mark 8 detected values are corrected usingthis correction curve F(X). In the fourth embodiment, the index mark 8is detected when the wafer mark is detected, and, therefore, an offsetused when detecting the wafer mark WM is calculated, and the wafer markdetected value is corrected using that offset. The technique employed bythe fourth embodiment is a combination of the processes shown in FIG. 12and FIG. 13. Although not shown in the drawing, step S201 is executedprior to step S101 in FIG. 13, and the position of the index mark 8 isdetected while the chamber 11 is at atmospheric pressure. In addition,step S202 is executed after step S301, and an offset calculated from theindex mark detected in step S301. Then, by executing steps S202 and S203instead of step S302, the offset is reflected in the wafer mark positiondetected in step S301, thus detecting the relative position of the wafermark relative to the index mark.

As described above, in the fourth embodiment of the present invention,the index mark can be detected at the same time the wafer mark isdetected, and, therefore, it is always possible to detect accurately therelative positions of the wafer and index marks, even if the pressuredifferential inside and outside the vacuum chamber 11 changes. As aresult, accurate alignment detection that reduces the impact of anaberration change can be executed even when the internal-externalchamber pressure differential changes. It should be noted that, by usingindex and alignment marks like those shown in FIGS. 7A and 7B, as in thethird embodiment, position detection of two axes intersecting atop thewafer can be carried out in a single image sensing.

Fifth Embodiment

In a fifth embodiment, oblique-incidence auto focus (AF) systemdetection is adapted to the mark position detection of the presentinvention.

FIG. 6 is a diagram showing the schematic structure of an alignmentdetection system of an exposure apparatus according to a fifthembodiment of the present invention. In FIG. 6, reference numeral 19designates an oblique-incidence AF detection illumination unit, 20designates an oblique-incidence AF detection mark, 21, 22 and 23designate focal optical systems, 27 designates a half mirror, 24designates an index mark illumination unit, 28 designates an index mark,25 designates an observation window, and 26 denotes an image sensingunit. An A/D converter 17 and an image sensing apparatus 18 are the sameas those in embodiments 1 through 4. It should be noted that, forsimplicity and clarity of description, FIG. 6 does not show theprojection optical system and the reticle necessary for exposure.

In this type of oblique-incidence AF system detection as well, as withthe methods described in the first embodiment and the third embodiment,by determining the relative positions of the oblique-incidence AFdetection mark and the index mark 28, it is always possible to conductaccurate AF detection (that is, detection of the position of a wafersurface along the projection optical system optical axis and/or theslant of the wafer surface with respect to the optical axis), even ifthe chamber housing as well as the observation window are deformed andthe alignment optical system optical axis is warped by the difference inpressure between the inside of the chamber and the outside of thechamber. In addition, by using the same methods described in the secondembodiment and the fourth embodiment, it is possible to correct anoffset occurring due to non-linear aberration even when such aberrationarises due to the difference in pressure between the inside and theoutside of the chamber. It should be noted that, although in FIG. 6, thedetection target object is a wafer, the arrangement is the same whendetecting the position of a reticle.

Sixth Embodiment

In a sixth embodiment, the mark detection of the present invention isadapted to reticle and wafer calibration. Here, a description is givenof an example in which, by detecting the relative positions of an indexmark and a reticle mark, as well as the relative positions of the indexmark and a wafer stage reference mark, respectively, the relativepositions of the reticle mark and the stage reference mark arecalibrated.

In FIG. 8, reference numeral 36 designates a calibration detectionillumination unit, 29 designates an index mark illumination unit, 30, 33and 37 designate focal optical systems, 31 designates an index mark, 32and 38 designate half mirrors, RST designates a reticle stage, Rdesignates a reticle, RM designates a reticle mark, ST designates astage, WSM designates a reference mark on the stage, 34 designates anobservation window, and 35 designates an image sensing unit.

In FIG. 8, when detecting the relative positions of the index mark 31and the stage reference mark WSM, a reticle stage RST is moved so that amirror 51 moves into the path of the light, thus enabling a light beamreflected from the wafer mark WSM to be focused on an image sensingsurface of the image sensing unit 35. By contrast, when detecting therelative positions of the index mark 31 and the reticle mark RM, thereticle stage RST is moved so that the reticle mark RM moves into thelight path and, at the same time, the stage ST is moved so that a mirror52 moves into the light path. By so doing, an alignment beam reflectedby the mirror 52 is reflected by mirrors 12, 13 so as to reach thereticle mark, and the light beam reflected from the reticle mark RM canbe focused on the image sensing surface of the image sensing unit 35.

Thus, as described above, the respective positions of the stagereference mark WSM and reticle mark RM can be determined using the indexmark as a reference, achieving the calibration described above. Inaddition, in the respective detections of the stage reference mark WSMand the reticle mark RM, by adapting the configuration of the firstembodiment, it is always possible to detect accurately the alignmentposition of a target object even when the chamber housing andobservation window are deformed, and the alignment optical systemoptical axis is warped due to a difference in pressure between theinside of the chamber and the outside of the chamber. Moreover, byadapting the mark detection technique of the second embodiment, anyoffset caused by non-linear aberration can be corrected, even if suchaberration is due to the difference in pressure between the inside andthe outside of the chamber occurs. Further, by adopting the constructionof the third and fourth embodiments, reliable calibration is alwayspossible, even in the face of changes in the internal-external chamberpressure differential.

It should be noted that, although in FIG. 8, the alignment beam isemitted from the reticle side, the present invention may be configuredso that, as shown in FIG. 9, the alignment beam originates at the waferside. In FIG. 9, when detecting the relative positions of the index mark31 and the stage reference mark WSM, the reticle stage RST is moved soas to move the mirror 51 into the path of the light. By contrast, whendetecting the relative positions of the index mark 31 and the reticlemark RM, the reticle stage RST is moved so as to move the reticle markRM into the light path and, on the wafer side, the stage ST is moved sothat a transparent glass portion 53 moves into the light path.

Seventh Embodiment

A seventh embodiment of the present invention adapts the mark detectionof the present invention to reticle alignment detection. In FIG. 10,reference numeral 46 designates a reticle alignment illumination unit,42 designates an index mark illumination unit, 39, 43 and 47 designatefocal optical systems, 44 designates an index mark, 45 and 48 designatehalf mirrors, RST designates a reticle stage, RSM designates a referencemark on the reticle stage, R designates a reticle, RM designates areticle mark, 40 designates an observation window and 41 designates animage sensing unit. In FIG. 10, the optical systems, wafer stage, andthe like, necessary for exposure have been omitted for simplicity andclarity of description.

In the reticle alignment of a reticle mark RM or a reticle referencemark RSM like that shown in FIG. 10 as well, by determining the relativepositions of the index mark 44 and the reticle reference mark RSM, or ofthe index mark 44 and the reticle mark RM, using the same methods asdescribed for the first and third embodiments, the correct alignmentmark position can always be detected, even if the chamber housing, aswell as the observation window, are deformed, and the alignment opticalsystem optical axis is warped by the difference in pressure between theinside of the chamber and the outside of the chamber. Moreover, by usingthe same method as that described for the second and fourth embodiments,any offset caused by non-linear aberration can be corrected, even ifsuch aberration due to the difference in pressure between the inside andthe outside of the chamber occurs.

It should be noted that, although in the foregoing embodiments, theindex mark and the detection target object mark (that is, the wafermark, reticle mark, wafer stage mark, reticle stage mark, AF detectionmark, or the like) are each illuminated by separate illumination units,the present invention may be configured so that light from a singleillumination unit is directed to each mark by a mirror, or the like. Inaddition, the present invention may be configured so that a commonillumination unit is used, and the index mark and the detection targetobject mark are disposed along a common light path.

Moreover, although in the mark position detection process describedabove, the two-dimensional mark image obtained using the image sensingunit is analyzed, the present invention is not limited to such anarrangement. Thus, for example, the present invention may be configuredto detect mark position based on a one-dimensional signal obtained by aline sensor (that is, a one-dimensional image signal).

Further, although in the foregoing embodiments, the index mark isprovided inside the chamber, even when the index mark is providedoutside the chamber, by using the methods described in the second andfourth embodiments, any mark position detection error can be corrected,even if the chamber housing, as well as the observation window aredeformed, and the alignment optical system optical axis is warped by thedifference in pressure between the inside of the chamber and the outsideof the chamber.

As described above, according to the embodiments, mark positiondetection error (that is, alignment detection error, oblique-incidenceAF detection error, etc.) caused by changes in observation windowdeformation and detection optical system aberration due to changes inthe internal-external chamber pressure differential can be reduced orcorrected.

Next, a description is given of a semiconductor device manufacturingprocess utilizing the exposure apparatus described above, using theexample of a device, such as a micro-device. FIG. 14 is a diagramshowing a device manufacturing process. In step 1 (circuit design), thedesign of the semiconductor device is carried out. In step 2 (maskproduction), a mask is produced based on the designed circuit pattern.

On the other hand, in step 3 (wafer manufacture), a wafer ismanufactured using a raw material, such as silicon. Step 4 (pre-process)is called pre-process, in which, using the mask and wafer describedabove, an actual circuit is formed on the wafer using a lithographictechnique according to the exposure apparatus described above. Thesucceeding step 5 (assembly) is called a post-process, and is a step inwhich a semiconductor chip is put together using the wafer produced instep 3, while also including such assembly processing as an assemblystep (dicing, bonding) and a packaging step (chip insertion). In step 6(inspection), the operation and durability of the semiconductor deviceproduced in step 5 are tested. Through such processes, a semiconductordevice is completed and, in step 7, shipped.

The wafer process of step 4 described above has the following steps: Astep of oxidizing the surface of the wafer, a CVD step of forming aninsulating layer on the wafer surface, an electrode formation step offorming an electrode on the wafer by vapor deposition, an ion injectionstep of injecting ions into the wafer, a resist process step of coatingthe wafer with a photosensitive agent, an exposure step of transferringto the wafer a circuit pattern after the resist process step using theexposure apparatus described above, a development step of developing thewafer exposed in the exposure step, an etching step of removing thoseportions other than the resist image developed in the developing step,and a resist peel step of removing excess resist after etching iscompleted. By repeating these steps, a multi-layered circuit pattern isbuilt up on the wafer.

According to the present invention, it is possible to detect with highaccuracy the position of a mark disposed inside a variable-pressurechamber by a sensor disposed outside the chamber. Thus, for example, theposition of a mark can be accurately detected, even if the chamberobservation window is warped by the difference in pressure inside thechamber and outside the chamber.

The present invention is not limited to the above-described embodiments,and various changes and modifications can be made thereto within thespirit and scope of the present invention. Therefore, to apprise thepublic of the scope of the present invention, the following claims aremade.

1-19. (canceled)
 20. A method of measuring a position of a mark in achamber, a pressure inside the chamber being different from a pressureoutside the chamber, said method comprising: a first detection step ofilluminating a reference mark fixedly disposed in the chamber using afirst illuminator disposed inside the chamber, and detecting thereference mark using a detector disposed outside the chamber; a seconddetection step of illuminating a mark movable with respect to thereference mark in the chamber using a second illuminator disposed insidethe chamber, and detecting the mark using the detector; and acalculation step of calculating a position of the mark with respect tothe reference mark based on detection results of the first and seconddetection steps.
 21. The method according to claim 20, wherein the firstilluminator and the second illuminator are the same unit.
 22. A methodof measuring a position of a mark in a chamber, said method comprising:a first detection step of detecting a reference mark fixedly disposed inthe chamber using a detector disposed outside the chamber, while apressure inside the chamber is equal to a pressure outside the chamber;a second detection step of detecting the reference mark using thedetector, with the pressure inside the chamber being different from thepressure outside the chamber; a third detection step of detecting a markmovable with respect to the reference mark in the chamber using thedetector, while the pressure inside the chamber is different from thepressure outside the chamber; and a correction step of correcting adetection result of the third detection step based on detection resultsof the first and second detection steps.
 23. An exposure apparatus forexposing a substrate to a pattern of an original, said apparatuscomprising: a chamber, having a window, adapted to accommodate theoriginal and the substrate, a pressure inside the chamber beingdifferent from a pressure outside the chamber; a reference mark fixedlydisposed in the chamber; and a mark disposed on one of the original, anoriginal stage holding the original, the substrate and a substrate stageholding the substrate, the mark movable with respect to the referencemark; a first illuminator disposed inside the chamber, adapted toilluminate the reference mark; a detector, disposed outside the chamber,adapted to detect positions of the reference mark and the mark throughthe window; and a calculation unit adapted to calculate a position ofthe mark with respect to the reference mark based on detection resultsof the reference mark and the mark.
 24. The apparatus according to claim23, wherein the first illuminator and the second illuminator are thesame unit.
 25. An exposure apparatus for exposing a substrate to apattern of an original, said apparatus comprising: a chamber, having awindow, adapted to accommodate the original and the substrate; areference mark fixedly disposed in the chamber; a mark disposed in thechamber, the mark movable with respect to the reference mark; adetector, disposed outside the chamber, adapted to detect positions ofthe reference mark and the mark through the window, the detectordetecting the reference mark while the pressure inside the chamber isequal to the pressure outside the chamber, and the detector detectingthe mark with the pressure inside the chamber being different from thepressure outside the chamber; and a correction unit adapted to correct adetection result of the mark based on detection results of the referencemark.
 26. A device manufacturing method comprising: a step of exposing asubstrate to a pattern of an original, using an exposure apparatus, theexposure apparatus comprising: (i) a chamber, having a window, adaptedto accommodate the original and the substrate, a pressure inside thechamber being different from a pressure outside the chamber; (ii) areference mark fixedly disposed in the chamber; (iii) a mark disposed onone of the original, an original stage holding the original, thesubstrate and a substrate stage holding the substrate, the mark movablewith respect to the reference mark; (iv) a first illuminator, disposedinside the chamber, adapted to illuminate the reference mark; (v) asecond illuminator, disposed inside the chamber, adapted to illuminatethe mark; (vi) a detector, disposed outside the chamber, adapted todetect positions of the reference mark and the mark through the window;and (vii) a calculation unit adapted to calculate a position of the markwith respect to the reference mark based on detection results of thereference mark and the mark.